Method for allocating and reserving resource for sidelink communication, and apparatus therefor

ABSTRACT

A method for transmitting data in sidelink communication, performed by a transmitting terminal, may comprise transmitting first control information including first resource allocation information for a first data transmission resource and second resource allocation information for a second data transmission resource; transmitting data through the first data transmission resource; transmitting second control information including the first resource allocation information for the first data transmission resource and the second resource allocation information for the second data transmission resource; and transmitting data through the second data transmission resource.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/932,531, filed on Jul. 17, 2020, and claimspriority to Korean Patent Applications No. 10-2019-0087895 filed on Jul.19, 2019, No. 10-2019-0135798 filed on Oct. 29, 2019, No.10-2020-0039928 filed on Apr. 1, 2020, and No. 10-2020-0074705 filed onJun. 19, 2020 with the Korean Intellectual Property Office (KIPO), theentire contents of which are hereby incorporated by reference.

BACKGROUND 1. Technical Field

The present disclosure relates generally to sidelink communicationmethods in a mobile communication system, and more specifically, tomethods for allocating and reserving resources for sidelinkcommunication, and apparatuses for the same.

2. Related Art

In the 3rd generation partnership project (3GPP), a new radio (NR)standardization phase 1 has been completed in Release-15, and astandardization phase 2 has been started in Release-16, so that newfeatures of the NR system are being discussed. One of the representativefunctions under discussion is NR vehicular-to-everything (V2X)communication. The V2X is a technology that supports communications invarious scenarios such as between vehicles, between a vehicle and aninfrastructure, and between a vehicle and a pedestrian based ondevice-to-device (D2D) communications of the long term evolution (LTE)system, and is also continuing to develop. The NR V2X is also beingdiscussed in the NR with the start of Release 16.

Three types of data transmission schemes are being discussed in the NRV2X. They are a unicast scheme for transmitting data to a specificterminal, a broadcast scheme for transmitting the same data to allterminals, and a groupcast scheme for transmitting data to a groupconsisting of a plurality of terminals. In the case of unicast datatransmission, a specific terminal receives data transmitted to itself,and transmits acknowledgement (ACK) or negative acknowledgment (NACK)feedback according to whether the data has been normally received ornot. When confirming that the ACK is transmitted as a result ofidentifying the ACK/NACK feedback, a transmitting terminal may determinethat the specific terminal has successfully received the data. On theother hand, when it is confirmed that the NACK is transmitted, thetransmitting terminal may determine that the specific terminal hasfailed to receive the data, and may transmit additional informationaccording to a HARQ scheme or retransmit the same data to increase theprobability of receiving the data at the specific terminal. In the caseof broadcast scheme of transmitting the same data to all terminals,since it is difficult to receive ACK/NACK feedbacks from all theterminals, and it is difficult to determine whether the data has beennormally received at each of all the terminals, the ACK/NACK feedbackprocedure is not usually applied. In case of system information, whichis representative information transmitted in the broadcast scheme, theACK/NCAK feedback procedure is not applied. Therefore, the systeminformation is periodically broadcast to solve the problem that itcannot be determined whether the data has been normally received at eachof all the terminals. In the case of the groupcast scheme newlydiscussed in the NR V2X, since information is transmitted to a pluralityof terminals, it is possible to periodically transmit necessaryinformation without the ACK/NACK feedback procedure as in the broadcastscheme. However, unlike the broadcast scheme, when the number of targetreceiving terminals are limited and the type of data is a type of datathat should be received within a predetermined time, efficient andstable data transmission and reception can be enabled by applying theACK/NACK feedback procedure similarly to the unicast scheme.

In addition, in case of power control for sidelink, a transmission powerof the transmitting terminal may be appropriately adjusted according toa transmission environment, thereby increasing data reliability at thereceiving terminal, and mitigating interferences to other terminals. Italso increases energy efficiency by reducing unnecessary transmissionpower usage. In the case of power control, there are an open-loop powercontrol scheme, in which the transmission power is set with a valuedetermined by a transmitting side in consideration of a givenconfiguration and a measured environment, and a closed-loop powercontrol scheme, in which the transmitting side adjusts a previously setpower value by receiving a transmit power control (TPC) command from areceiving side of data.

SUMMARY

Accordingly, exemplary embodiments of the present disclosure providemethods for transmitting data for sidelink communication.

Accordingly, exemplary embodiments of the present disclosure providemethods for receiving data for sidelink communication.

Accordingly, exemplary embodiments of the present disclosure provide aterminal apparatus for sidelink communication.

According to an exemplary embodiment of the present disclosure, a methodfor transmitting data in sidelink communication, performed by atransmitting terminal, may comprise transmitting first controlinformation including first resource allocation information for a firstdata transmission resource and second resource allocation informationfor a second data transmission resource; transmitting data through thefirst data transmission resource; transmitting second controlinformation including the first resource allocation information for thefirst data transmission resource and the second resource allocationinformation for the second data transmission resource; and transmittingdata through the second data transmission resource.

The first control information and the second control information mayredundantly indicate the first resource allocation information for thefirst data transmission resource and the second resource allocationinformation for the second data transmission resource.

A maximum number of resource allocation information for datatransmission resources, which each of the first control information andthe second control information is capable of including, may beconfigured by a base station.

Each of the first control information and the second control informationmay include information indicating which order each configurationinformation has within the maximum number.

Data transmission resources indicated by the maximum number of resourceallocation information may be located within a predetermined timeperiod.

Each of the first control information and the second control informationmay be a first stage sidelink control information (SCI).

According to another exemplary embodiment of the present disclosure, amethod for receiving data in sidelink communication, performed by areceiving terminal may comprise detecting first control informationincluding first resource allocation information for a first datatransmission resource and second resource allocation information for asecond data transmission resource; when the first control information issuccessfully received, receiving data through the first datatransmission resource; detecting second control information includingthe first resource allocation information for the first datatransmission resource and the second resource allocation information forthe second data transmission resource; and when the second controlinformation is successfully received, receiving data through the seconddata transmission resource.

The first control information and the second control information mayredundantly indicate the first resource allocation information for thefirst data transmission resource and the second resource allocationinformation for the second data transmission resource.

A maximum number of resource allocation information for datatransmission resources, which each of the first control information andthe second control information is capable of including, may beconfigured by a base station.

Each of the first control information and the second control informationmay include information indicating which order each configurationinformation has within the maximum number.

Data transmission resources indicated by the maximum number of resourceallocation information may be located within a predetermined timeperiod.

Each of the first control information and the second control informationmay be a first stage SCI.

The method may further comprise, when the first control information isnot successfully received, receiving data through the first datatransmission resource indicated by the first resource allocationinformation of the second control information.

The method may further comprise, when the second control information isnot successfully received, receiving data through the second datatransmission resource indicated by the second resource allocationinformation of the first control information.

According to another exemplary embodiment of the present disclosure, aterminal in sidelink communication may comprise a processor; a memoryelectronically communicating with the processor; and instructions storedin the memory, wherein when executed by the processor, the instructionscause the terminal to: transmit first control information includingfirst resource allocation information for a first data transmissionresource and second resource allocation information for a second datatransmission resource; transmit data through the first data transmissionresource; transmit second control information including the firstresource allocation information for the first data transmission resourceand the second resource allocation information for the second datatransmission resource, and transmit data through the second datatransmission resource.

The first control information and the second control information mayredundantly indicate the first resource allocation information for thefirst data transmission resource and the second resource allocationinformation for the second data transmission resource.

A maximum number of resource allocation information for datatransmission resources, which each of the first control information andthe second control information is capable of including, may beconfigured by a base station.

Each of the first control information and the second control informationmay include information indicating which order each configurationinformation has within the maximum number.

Data transmission resources indicated by the maximum number of resourceallocation information may be located within a predetermined timeperiod.

Each of the first control information and the second control informationmay be a first stage SCI.

Using various exemplary embodiments of the present disclosure, sidelinkcommunication can be efficiently performed. In particular, whenimportant control information is redundantly transmitted, the receivingterminal can successfully receive data even when only one of theredundantly transmitted control information is received. In addition,even when only one of the redundantly transmitted control information isreceived, the position of the reserved resource within a predeterminedtime period can be known, thereby reducing collisions of reservedresources between terminals. Therefore, the performance of thecommunication system can be improved.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments of the present disclosure will become moreapparent by describing in detail embodiments of the present disclosurewith reference to the accompanying drawings, in which:

FIG. 1 is a conceptual diagram illustrating a type 1 frame structure inthe LTE system:

FIG. 2 is a conceptual diagram illustrating a type 2 frame structure inthe LTE system;

FIG. 3 is a conceptual diagram for describing transmission of an SSburst set in an NR system;

FIG. 4 is a conceptual diagram for describing a synchronization signalblock configuration of an NR system:

FIG. 5 is a conceptual diagram for describing an example of dividing awideband component carrier (CC) into a plurality of bandwidth parts(BWP) and transmitting SSBs in each BWP in an NR system;

FIG. 6 is a conceptual diagram for describing three basic patterns forconfiguring an RMSI CORESET in an NR system:

FIG. 7 is a conceptual diagram for describing channel multiplexing in asidelink communication system;

FIGS. 8A and 8B are conceptual diagrams for describing a first exemplaryembodiment of channel multiplexing in a communication system accordingto the present disclosure;

FIG. 9 is a conceptual diagram for describing a second exemplaryembodiment of channel multiplexing in a communication system accordingto the present disclosure:

FIGS. 10 to 12 are conceptual diagrams for describing transmissionresource allocation in a communication system; and

FIG. 13 is a block diagram illustrating a configuration of an apparatusfor performing methods according to exemplary embodiments of the presentdisclosure.

It should be understood that the above-referenced drawings are notnecessarily to scale, presenting a somewhat simplified representation ofvarious preferred features illustrative of the basic principles of thedisclosure. The specific design features of the present disclosure,including, for example, specific dimensions, orientations, locations,and shapes, will be determined in part by the particular intendedapplication and use environment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure are disclosed herein. However,specific structural and functional details disclosed herein are merelyrepresentative for purposes of describing embodiments of the presentdisclosure. Thus, embodiments of the present disclosure may be embodiedin many alternate forms and should not be construed as limited toembodiments of the present disclosure set forth herein.

Accordingly, while the present disclosure is capable of variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and will herein be described indetail. It should be understood, however, that there is no intent tolimit the present disclosure to the particular forms disclosed, but onthe contrary, the present disclosure is to cover all modifications,equivalents, and alternatives falling within the spirit and scope of thepresent disclosure. Like numbers refer to like elements throughout thedescription of the figures.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(i.e., “between” versus “directly between,”-adjacent” versus “directlyadjacent,” etc.).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this present disclosure belongs.It will be further understood that terms, such as those defined incommonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in greater detail with reference to the accompanying drawings.In order to facilitate general understanding in describing the presentdisclosure, the same components in the drawings are denoted with thesame reference signs, and repeated description thereof will be omitted.

The 3GPP Long Term Evolution (LTE) system, which is one of theconventional mobile communication technologies, supports three types offrame structures. The first is a type 1 frame structure applicable toFrequency Division Duplex (FDD), the second is a type 2 frame structureapplicable to Time Division Duplex (TDD), and the last is a type 3 framestructure for transmission in an unlicensed frequency band.

FIG. 1 is a conceptual diagram illustrating a type 1 frame structure inthe LTE system.

Referring to FIG. 1, one radio frame may have a length of 10 ns (307,200Ts), and comprise 10 subframes. Here, T_(s) is a sampling time and has avalue of 1/(15 kHz×2048). Each subframe has a length of 1 ms, and onesubframe includes two slots each having a length of 0.5 ms. One slotconsists of seven OFDM symbols in case of a normal CP and six OFDMsymbols in case of an extended CP.

FIG. 2 is a conceptual diagram illustrating a type 2 frame structure inthe LTE system.

Referring to FIG. 2, the relationship among a radio frame, subframes,and slots, and their lengths are the same as in the case of type 1. As adifference, one radio frame may be composed of downlink subframe(s),uplink subframe(s), and special subframe(s). The special subframe(s) mayexist between a downlink subframe and an uplink subframe, and mayinclude a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP), and anUplink Pilot Time Slot (UpPTS). One radio frame may include two specialsubframes when a downlink-uplink switching periodicity is 5 ms, and onespecial subframe when the downlink-uplink switching periodicity is 10ms. The DwPTS may be used for cell search, synchronization, or channelestimation, and the GP may be a period for removing interferencegenerated in uplink of a base station due to a multipath delaydifference of terminals. In the UpPTS, a Physical Random Access Channel(PRACH) or a Sounding Reference Signal (SRS) may be transmitted.

In the LTE system, a Transmission Time Interval (TTI) means a basic timeunit in which an encoded data packet is transmitted through a physicallayer signal. The LTE release 14 defines short TTI-based datatransmission to meet low latency requirements. To distinguish the TTI upto release 14 from the short TTI, the TTI up to release 14 may bereferred to as a ‘base TTI’ or ‘regular TTI’.

The base TTI of the LTE system consists of one subframe. That is, a timeaxis length of a Physical Resource Block (PRB) pair, which is a minimumunit of resource allocation, is 1 ms. In order to support transmissionof the 1 ms TTI, physical signals and channels are also mostly definedon a subframe basis. For example, a Cell-specific Reference Signal(CRS), a Physical Downlink Control Channel (PDCCH), a Physical DownlinkShared Channel (PDSCH), a Physical Uplink Control Channel (PUCCH) and aPhysical Uplink Shared Channel (PUSCH) may exist for each subframe. Onthe other hand, a Primary Synchronization Signal (PSS) and a SecondarySynchronization Signal (SSS) may be present in every fifth subframe, anda Physical Broadcast Channel (PBCH) may be present in every tenthsubframe. Meanwhile, one radio frame consists of 10 subframes and has atime axis length of 10 ms. The radio frame is identified by a SystemFrame Number (SFN), which is used to define transmission of a signal(e.g., paging, channel estimation reference signal, channel stateinformation reporting) having a transmission periodicity longer than oneradio frame. A periodicity of the SFN is 1024.

In the LTE system, the PBCH is a physical layer broadcast channel thatconveys the most essential system information called a MasterInformation Block (MIB). The PBCH is transmitted every tenth subframeand is transmitted once in one radio frame. The MIB should betransmitted with the same information during four radio frames, afterwhich it may change depending on the situation of the system. This iscalled a PBCH TTI (=40 ms) for convenience. In this case, thetransmitted MIB includes 3 bits indicating a system band, 3 bits relatedto a Physical Hybrid ARQ Indicator Channel (PHICH), 8 bits for the SFN,10 bits reserved for future use, and 16 bits for a cyclic redundancycheck (CRC). That is, the MIB is comprised of a total of 40 bits. TheSFN identifying the radio frame consists of a total of 10 bits (B9˜B0),and only 8 bits (B9˜B2) that are most significant bits (MSB) of the SFNare transmitted through the PBCH. Accordingly, the information on thecorresponding SFN, which is transmitted through the PBCH, is not changedduring four radio frames. The remaining 2 bits (B1˜B0) that are leastsignificant bits (LSB) of the SFN changing during four radio frames areimplied through a scrambling sequence used for the PBCH without beingexplicitly given by the MIB transmitted through the PBCH. As thescrambling sequence of the PBCH, a gold sequence generated by beinginitialized with a cell identifier (ID) is used, and the PBCH scramblingsequence is newly initialized by an equation of mod (SFN, 4) with aperiodicity of four radio frames. Therefore, a gold sequence, which isnewly generated by being initialized with a cell ID for each radio framewhose LSB 2-bits of the SFN is ‘00’, is applied as the scramblingsequence. Gold sequences, which are generated successively thereafter,are used for PBCH scrambling in radio frames whose 2 bits of the SFNends with ‘01’, ‘10’, and ‘11’. Accordingly, the terminal acquiring acell ID during an initial cell search may implicitly identifyinformation on ‘00’, ‘01’, ‘10’, or ‘11’ of the LSB 2 bits of the SFNthrough the scrambling sequence during the PBCH decoding. The terminalmay finally identify 10 bits (B9˜B0) of the SFN by combining two bits(B1˜B0) obtained through the scrambling sequence and 8 bits (B9˜B2)obtained explicitly through the PBCH.

The evolved mobile networks after the LTE should meet technicalrequirements to support a wider range of service scenarios, as well asthe high transmission speeds that were previously a major concern.Recently, the ITU-R has defined key performance indicators (KPIs) andrequirements for the IMT-2020, the official name for 5G mobilecommunications. These are summarized as enhanced mobile broadband(eMBB), ultra reliable low latency communication (URLLC), and massivemachine type communication (mMTC). The planned schedule of the ITU-Raims to distribute frequencies for the IMT-2020 in year 2019 andcomplete international standard approval by year 2020.

The 3GPP is developing 5G standard specifications based on a new radioaccess technology (RAT) that meets the requirements of IMT-2020.According to the definition of 3GPP, the new radio access technology isa radio access technology that does not have backward compatibility withthe existing 3GPP radio access technology. The new wirelesscommunication system after the LTE adopting such the radio accesstechnology will be referred to herein as a new radio (NR).

As waveform technologies for the NR, candidates such as orthogonalfrequency division multiplexing (OFDM), filtered OFDM, generalizedfrequency division multiplexing (GFDM), filter bank multi-carrier(FBMC), and universal filtered multi-carrier (UFMC) are being discussed.Although there are advantages and disadvantages, cyclic prefix (CP)based OFDM and single carrier-frequency division multiple access(SC-FDMA) are still effective schemes for 5G systems due to therelatively low implementation complexity and multiple-inputmultiple-output (MIMO) scalability. However, in order to flexiblysupport various 5G usage scenarios, a method of simultaneouslyaccommodating various waveform parameters in one carrier without guardbands may be considered. To this end, the filtered OFDM, the GFDM, orthe like having a frequency spectrum with low out of band emission (OOB)may be suitable.

In the present invention, for convenience of description, it is assumedthat the CP-based OFDM (CP-OFDM) is a waveform technology for wirelessaccess. However, this is merely for convenience of description, and thescope of the claims of the present invention is not limited to aspecific waveform technology. In general, the category of CP-based OFDMtechnology includes the filtered OFDM or the spread spectrum OFDM (e.g.,DFT-spread OFDM) technology.

One of the biggest factors determining a subcarrier spacing of an OFDMsystem is a carrier frequency offset (CFO) experienced by a receiver,which is characterized by an increase in proportion to an operatingfrequency due to a Doppler effect and a phase drift. Therefore, in orderto prevent performance degradation due to the carrier frequency offset,the subcarrier spacing should increase in proportion to the operatingfrequency. On the other hand, if the subcarrier spacing is too large,there is a disadvantage that the CP overhead increases. Therefore, thesubcarrier spacing should be defined as an appropriate value consideringchannel and RF characteristics for each frequency band.

Various numerologies are considered in the NR system. For example, thesubcarrier spacing of 15 kHz, which is the subcarrier spacing of theconventional LTE, and the subcarrier spacings of 30 kHz, 60 kHz, and 120kHz, which respectively are 2, 4, and 8 times scaled, may be consideredtogether. Configuring the differences between the subcarrier spacings ofdifferent numerologies by exponential multipliers of 2 may beadvantageous for heterogeneous numerology-based carrier aggregation,frame structure design, and multiplexing of heterogeneous numerologywithin one carrier.

The NR system is expected to be used in a wide range of frequenciesranging from hundreds of MHz to tens of GHz. In general, since thediffraction and reflection characteristics of radio waves are not goodat high frequencies, propagation characteristics are generally not good,and propagation losses such as path loss and reflection loss are knownto be relatively large compared to those of the low frequencies.Therefore, when the NR system is deployed in the high frequency, cellcoverage may be reduced as compared with the existing low frequency. Inorder to solve this problem, a method of increasing cell coveragethrough beamforming using a plurality of antenna elements may beconsidered at high frequency.

The beamforming schemes may include an analog beamforming scheme and adigital beamforming scheme. The digital beamforming scheme may obtain abeamforming gain by using a plurality of radio frequency (RF) pathsbased on multiple input multiple output (MIMO) and a digital precoder ora codebook. The analog beamforming scheme may obtain a beamforming gainthrough an antenna array and a number of analog and RF devices such asphase shifters, power amplifiers (PAs), and variable gain amplifiers(VGAs). Since the digital beamforming scheme requires adigital-to-analog converter (DAC) or an analog-to-digital converter(ADC) and requires the same number of transceiver units (TXRUs) asantenna elements, increase of the beamforming gain proportionallyincreases the complexity of the antenna implementation as well. In theanalog beamforming scheme, since a plurality of antenna elements areconnected to a single transceiver unit through phase shifters, even whenthe number of antenna elements is increased in order to increase thebeamforming gain, the resulting complexity is not greatly increased.However, the performance of the analog beamforming scheme is lower thanthat of the digital beamforming scheme, and the frequency resourceutilization efficiency is limited because the phase shifters arecontrolled in time domain. Therefore, a hybrid beamforming scheme, whichis a combination of the analog scheme and the digital scheme, may beused.

In the case that the cell coverage is increased through the beamforming,not only dedicated control channels and dedicated data for each terminalin the cell but also common control channels and common signals for allterminals in the cell may be also transmitted in the beamforming manner.When the common control channels and signals are transmitted to allterminals by applying the beamforming to increase the cell coverage,since the common control channels and signals cannot be transmitted toall the regions in the cell through a single transmission, they may betransmitted through a plurality of beams over a plurality of times for apredetermined time. Transmitting multiple times by switching multiplebeams is called beam sweeping. Such the beam sweeping operation isnecessarily required when transmitting common control channels andsignals using the beamforming.

A terminal accessing the system acquires downlink frequency/timesynchronization and a cell ID through a synchronization signal (SS),acquires uplink synchronization through a random access procedure, andestablishes a link. In this case, in the NR system, TDM-basedmultiplexing of an NR-SS and an NR-PBCH which are periodicallytransmitted is supported, and they are transmitted using N(=4) OFDMsymbols. These N OFDM symbols are defined as an SS block (SSB). In caseof transmitting the SSBs using beamforming, a beam sweeping operationthat transmits multiple beams while switching the multiple beams isrequired. For this, a plurality of SSBs may be defined within atransmission period of the NR-SS and the NR-PBCH, and the plurality ofSSBs configured as described above are assembled into an SS burst set.

FIG. 3 is a conceptual diagram for describing transmission of an SSburst set in an NR system.

Referring to FIG. 3, an SS burst set is repeated periodically. Accordingto a periodicity of the SS burst set, the base station transmits SSBs tothe terminals in the cell through different beams in a beam sweepingmanner. The maximum number L of SSBs constituting one SS burst set andthe locations of the L SSBs are defined in the specification, and L mayhave a different value according to a system frequency region. Thenumber and locations of SSBs actually transmitted among the L SSBs maybe determined by a network.

FIG. 4 is a conceptual diagram for describing a synchronization signalblock configuration of an NR system.

Referring to FIG. 4, signals and a channel are time division multiplexedin one SSB in the order of PSS, PBCH, SSS, and PBCH, and the PBCH may betransmitted in both end bands adjacent to the frequency band in whichthe SSS is transmitted. Also, an SSB index may be identified through aPBCH DMRS when the maximum number L of SSBs is 8 in the sub 6 GHzfrequency band. When the maximum number L of SSBs is 64 in the over 6GHz frequency band. LSB 3 bits of 6 bits representing the SSB index isidentified through the PBCH DMRS, and the remaining MSB 3 bits aretransmitted through a payload of the PBCH, which are identified byperforming decoding on the PBCH.

The NR system can support a system bandwidth of up to 400 MHz, but incase of a terminal, the size of bandwidth that can be supported may varyaccording to the capability of the terminal. Therefore, some terminalsaccessing the wideband system can access only part of the entire band ofthe system. In order to facilitate connection of terminals supportingvarious bandwidths in a system supporting such a wide bandwidth, unlikethe conventional LTE, which always transmits synchronization signals andPBCHs at the center of the system bandwidth, the NR system may transmitSSBs in multiple locations in the frequency axis.

FIG. 5 is a conceptual diagram for describing an example of dividing awideband component carrier (CC) into a plurality of bandwidth parts(BWP) and transmitting SSBs in each BWP in an NR system.

Referring to FIG. 5, a terminal may perform initial access using one ofSSBs transmitted through each BWP. After detecting of an SSB, theterminal may perform a cell access procedure by acquiring RemainingMinimum System Information (RMSI), and the RMSI may be transmitted in aPDSCH through scheduling by a PDCCH. In this case, configurationinformation of a Control Resource Set (CORESET) in which the PDCCHcontaining scheduling information of a RMSI PDSCH is transmitted istransmitted through a PBCH in the SSB. When multiple SSBs aretransmitted in the entire system band, some SSBs may have RMSIsassociated therewith, and some SSBs may not have RMSIs associatedtherewith. In this case, the SSB having the associated RMSI is definedas a ‘cell defining SSB’, and the cell search and initial accessprocedure of the terminal may be performed only through the ‘celldefining SSB’. The SSBs not having the associated RMSI may be used forperforming synchronization or measurement in the corresponding BWP. Inthis case, the BWP in which the SSB is transmitted may be limited tosome of several BWPs in the wideband.

As described above, the reception of RMSI is performed through a seriesof processes of detecting a PDCCH through the CORESET configurationinformation transmitted through a PBCH, obtaining scheduling informationof an RMSI from the PDCCH, and receiving a PDSCH accordingly. In thiscase, a control channel resource region through which the PDCCH can betransmitted is configured through RMSI CORESET configurationinformation, which may have three patterns as follows.

FIG. 6 is a conceptual diagram for describing three basic patterns forconfiguring an RMSI CORESET in an NR system.

In order to configure an RMSI CORESET, one of three patterns shown inFIG. 6 is selected, and detailed configuration is completed in theselected pattern. In the pattern 1, SSB, RMSI CORESET, and RMSI PDSCHare all TDMed. In the pattern 2, RMSI CORESET and RMSI PDSCH are TDMed,and only RMSI PDSCH is frequency division multiplexed (FDMed) with SSB.In the pattern 3, RMSI CORESET and RMSI PDSCH are TDMed, and both RMSICORESET and RMSI PDSCH are FDMed with SSB. Only the pattern 1 can beused in the frequency band below 6 GHz, and the patterns 1, 2, and 3 canbe used in the frequency band above 6 GHz. Also, the numerologies usedfor SSB. RMSI CORESET, and RMSI PDSCH may differ. For the pattern 1, allcombinations of numerologies can be used. For the pattern 2, onlycombinations of {SSB, RMSI}, which include {120 kHz, 60 kHz} and {240kHz, 120 kHz}, can be used. For the pattern 3, only a combination of(SSB, RMSI), which is {120 kHz, 120 kHz}, can be used.

The RMSI CORESET configuration information selects one of the threepatterns according to a combination of numerologies for SSB and RMSI.The RMSI CORESET configuration information may be configured using TableA representing the number of resource blocks (RBs) of the RMSI CORESET,the number of symbols of the CORESET, and information on an offsetbetween an RB of the SSB and an RB of the RMSI CORESET, and Table Brepresenting the number of search space sets per slot for each patternand information for configuring a monitoring occasion of RMSI PDCCH suchas a CORESET offset, an OFDM symbol index, and the like. Each of TablesA and B actually consists of several tables (Table A: Table 13-1 toTable 13-8, Table B: Table 13-9 to Table 13-13). The RMSI CORESETconfiguration information is configured with 4 bits from each of TablesA and B. and represents information of 8 bits.

In the NR system, a PDSCH may be transmitted using one of two timedomain mapping types. The two mapping types are Type A and Type B, andare defined as Table 1 below.

TABLE 1 PDSCH mapping Normal CP Extended CP type S L S + L S L S + LType A {0, 1, 2, 3} {3, . . . , 14} {3, . . . , 14} {0, 1, 2, 3} {3, . .. , 12} {3, . . . , 12} (Note 1) (Note 1) Type B {0, . . . , 12} {2, 4,7} {2, . . . , 14} {0, . . . , 10} {2, 4, 6} {2, . . . , 12} (Note 1): S= 3 is applicable only if dmrs-TypeA-Position = 3

The type A is a slot-based transmission, and the position of the symbolwhere a PDSCH starts may be set to one of {0, 1, 2, 3}. The number ofsymbols where the PDSCH is transmitted may be set to one of 3 to 14within a range not exceeding a slot boundary in case of a normal CP. Thetype B is a non-slot-based transmission, and the position of the symbolswhere the PDSCH starts may be set to one of 0 to 12. The number ofsymbols where the PDSCH is transmitted may be set to one of {2, 4, 7}within a range not exceeding a slot boundary in case of a normal CP. Inthis case, a DM-RS for data demodulation of the PDSCH is determined by avalue of ld indicating the type A and the type B resource allocationscheme and a length, and the value of ld may be defined differentlyaccording to the type A and type B resource allocation scheme.

As NR phase 1 standardization has been finalized in 3GPP release 15 andphase 2 standardization is proceeding in release 16, new features forthe NR system are being discussed. The representative one among them isNR-Unlicensed (NR-U). The NR-U is a technology to support operations inan unlicensed spectrum used in communication systems such as Wi-Fi toincrease network capacity by increasing utilization of limited frequencyresources. The 3GPP communication system for operations in an unlicensedband has begun standardization with Licensed-Assisted Access (LTE-LAA)technology in 3GPP release 13, and has continued to evolve to release 14‘Enhanced LAA (LTE-eLAA)’ and release 15 ‘Further Enhanced LAA(LTE-FeLAA)’. Also in the NR, a standardization work is proceedingthrough a work item (WI) in the release 16 started from a study item(SI) for the NR-U.

In the NR-U, similarly to the general NR system, terminals can determinewhether a base station (e.g., gNB) transmits a signal based on adiscovery reference signal (DRS) transmitted from the base station. Inparticular, in the NR-U of a stand-alone (SA) mode, the terminal mayacquire synchronization and system information through the DRS. In theNR-U system, the transmission of the DRS should comply with theregulation for the use of the unlicensed band (e.g., transmission bandand transmission power, and transmission time). In particular, when asignal is transmitted in the unlicensed band, the transmission signalshould be configured and transmitted to occupy 80% of the total channelbandwidth (e.g., 20 MHz) according to the occupied channel bandwidth(OCB) regulation.

In addition, in the case of the NR-U, a Listen-Before-Talk (LBT)procedure should be performed for coexistence with other systems due tothe characteristics of the unlicensed band in order to transmit a signaland data as well as the DRS. The LBT procedure is a procedure foridentifying whether another base station, another terminal, or anothersystem is transmitting a signal before transmitting a signal. The basestation or terminal of the NR-U system may determine whether a signal istransmitted or not for a predetermined time period through the LBTprocedure, and may transmit its own signal when it is determined that nosignal is transmitted. When the LBT procedure fails, the base station orterminal may not transmit a signal. Depending on the type of signal tobe transmitted, various categories of LBT procedures may be performedbefore transmission of the corresponding signal.

Also, as the standardization phase 2 has been started in Release-16, newfeatures of the NR system are being discussed. One of the representativefunctions under discussion is NR vehicular-to-everything (V2X)communication. The V2X is a technology that supports communications invarious scenarios such as between vehicles, between a vehicle and aninfrastructure, and between a vehicle and a pedestrian based ondevice-to-device (D2D) communications of the long term evolution (LTE)system, and is also continuing to develop. The NR V2X is also beingdiscussed in the NR with the start of Release 16.

Three types of data transmission schemes are being discussed in the NRV2X. They are a unicast scheme for transmitting data to a specificterminal, a broadcast scheme for transmitting the same data to allterminals, and a groupcast scheme for transmitting data to a groupconsisting of a plurality of terminals. In the case of unicast datatransmission, a specific terminal receives data transmitted to itself,and transmits acknowledgement (ACK) or negative acknowledgment (NACK)feedback according to whether the data has been normally received ornot. When confirming that the ACK is transmitted as a result ofidentifying the ACK/NACK feedback, a transmitting terminal may determinethat the specific terminal has successfully received the data. On theother hand, when it is confirmed that the NACK is transmitted, thetransmitting terminal may determine that the specific terminal hasfailed to receive the data, and may transmit additional informationaccording to a HARQ scheme or retransmit the same data to increase theprobability of receiving the data at the specific terminal. In the caseof broadcast scheme of transmitting the same data to all terminals,since it is difficult to receive ACK/NACK feedbacks from all theterminals, and it is difficult to determine whether the data has beennormally received at each of all the terminals, the ACK/NACK feedbackprocedure is not usually applied. In case of system information, whichis representative information transmitted in the broadcast scheme, theACK/NCAK feedback procedure is not applied. Therefore, the systeminformation is periodically broadcast to solve the problem that itcannot be determined whether the data has been normally received at eachof all the terminals. In the case of the groupcast scheme newlydiscussed in the NR V2X, since information is transmitted to a pluralityof terminals, it is possible to periodically transmit necessaryinformation without the ACK/NACK feedback procedure as in the broadcastscheme. However, unlike the broadcast scheme, when the number of targetreceiving terminals are limited and the type of data is a type of datathat should be received within a predetermined time, efficient andstable data transmission and reception can be enabled by applying theACK/NACK feedback procedure similarly to the unicast scheme.

In addition, in case of power control for sidelink, a transmission powerof the transmitting terminal may be appropriately adjusted according toa transmission environment, thereby increasing data reliability at thereceiving terminal, and mitigating interferences to other terminals. Italso increases energy efficiency by reducing unnecessary transmissionpower usage. In the case of power control, there are an open-loop powercontrol scheme, in which the transmission power is set with a valuedetermined by a transmitting side in consideration of a givenconfiguration and a measured environment, and a closed-loop powercontrol scheme, in which the transmitting side adjusts a previously setpower value by receiving a transmit power control (TPC) command from areceiving side of data.

It may be difficult due to various causes including a multipath fadingchannel, interference, and the like to predict a received signalstrength at the receiving terminal. Accordingly, the receiving terminalmay adjust a receive power level (e.g., receive power range) byperforming an automatic gain control (AGC) operation to prevent aquantization error of the received signal and maintain a proper receivepower. In the communication system, the terminal may perform the AGCoperation using a reference signal received from the base station.However, in the sidelink communication (e.g., V2X communication), thereference signal may not be transmitted from the base station. That is,in the sidelink communication, communication between terminals may beperformed without the base station. Therefore, it may be difficult toperform the AGC operation in the sidelink communication. In the sidelinkcommunication, the transmitting terminal may first transmit a signal(e.g., reference signal) to the receiving terminal before transmittingdata, and the receiving terminal may adjust a receive power range (e.g.,receive power level) by performing an AGC operation based on the signalreceived from the transmitting terminal. Thereafter, the transmittingterminal may transmit sidelink data to the receiving terminal. Thesignal used for the AGC operation may be a signal duplicated from asignal to be transmitted later or a signal preconfigured between theterminals.

In the NR-V2X communication, retransmission may be performed by apredetermined number of times according to a predetermined procedureregardless of whether or not reception is successful in order toincrease reception reliability of a data transmission/receptionprocedure through a sidelink. In this case, there is no need to transmita feedback according to whether reception is successful. Alternatively,a receiving terminal may transmit a feedback according to whetherreception is successful, and a transmitting terminal may performretransmission accordingly. When a receiving terminal transmits afeedback according to whether reception is successful or not and atransmitting terminal performs retransmission accordingly, the receivingterminal should transmit acknowledgment (ACK) or negative ACK (NACK)feedback information to the transmitting terminal according to whetherdata has been successfully received. On the other hand, the transmittingterminal should monitor the feedback information from the receivingterminal to determine whether to retransmit the data. In general, suchthe transmission and monitoring of the feedback information may beperformed in a point-to-point scheme at the receiving side and thetransmitting side of data. However, in case of the sidelinkcommunication, which is communication between terminals, since atransmitting terminal can autonomously select a resource and a receivingterminal without control of the base station, a transmission time and areception time of feedback information for a specific terminal mayoverlap. In addition, one terminal may simultaneously transmit feedbackinformation to multiple terminals, and one terminal may simultaneouslytransmit feedback information for multiple data units received fromanother terminal.

For sidelink communication in the NR-V2X, transmission of a data channelfor actual data transmission and transmission of a control channelincluding scheduling information for resource allocation of the datachannel are required. In the sidelink communication, a physical sidelinkshared channel (PSSCH) may be used as a data channel, and a physicalsidelink control channel (PSCCH) may be used as a control channel. Thedata channel and the control channel may be multiplexed and transmittedin the time and frequency resource domain. In the NR-V2Xstandardization, various multiplexing schemes have been discussed, andthe option 3, which will be described later, may be basically supported.

Channel Multiplexing for Sidelink Communication

FIG. 7 is a conceptual diagram for describing channel multiplexing in asidelink communication system.

As shown in FIG. 7, the multiplexing schemes of a PSCCH that is asidelink control channel and a PSSCH that is a sidelink data channel maybe classified into an option 1A/B in which the PSCCH and the PSSCH aretime division multiplexed (TDMed), an option 2 in which the PSCCH andthe PSSCH are frequency division multiplexed (FDMed), and an option 3 inwhich the PSCCH and the PSSCH are time/frequency multiplexed.

Referring to FIG. 7, in the NR-V2X sidelink communication, a sub-channelmay be used as a basic unit of resource configuration. The sub-channelmay be defined as a predetermined time and frequency resource, and maybe composed of a plurality of OFDM symbols and a plurality of resourceblocks (RBs) in the time and frequency domain. In general, a datachannel and a control channel within the sub-channel may be multiplexedin the option 3 scheme of FIG. 7.

When a plurality of sub-channels are allocated for data communication toa specific terminal, a data channel and a control channel may bemultiplexed in all sub-channels allocated to the terminal or multiplexedonly in a specific sub-channel. When the data channel and the controlchannel are multiplexed in all sub-channels, it may be advantageous tosecure resources for transmission of control channels. However, whenthere is no prior information on how many sub-channels are allocated tothe terminal, complexity may be increased because blind detection of aplurality of sub-channels should be performed. Further, even when aplurality of sub-channels need to be allocated according to the size ofthe data to be transmitted, the size of control information required totransmit the data may not be increased in proportion to the size of thedata, and in general, it may be maintained constantly.

Accordingly, in an exemplary embodiment of the present disclosure, evenwhen a plurality of sub-channels are allocated for data transmission toa specific terminal, the data channel and the control channel may alwaysbe multiplexed only in a specific sub-channel(s). That is, the controlchannel transmitted to the corresponding terminal may always betransmitted as limited to a specific sub-channel(s). More specifically,the specific sub-channel(s) may be sub-channel(s) having the smallestindex, the largest index, or a statically determined index among thesub-channels allocated to the corresponding terminal. For example, whensub-channels #n, #n+1, #n+2, and #n+3 are allocated to a specificterminal, if the control channel is transmitted only through thesub-channel(s) having the smallest index, the control channel may betransmitted only in the sub-channel #n as multiplexed with the datachannel, and only the data channel may be transmitted in the remainingsub-channels #n+1, #n+2, and #n+3. When the control channel istransmitted through only one sub-channel, if a channel state of aresource region that is limitedly used for transmission of the controlchannel in the corresponding sub-channel is not good, or the resourcefor transmitting the control channel carrying important controlinformation is insufficient within the sub-channel, the control channelmay be transmitted as extended to the next sub-channel region.Specifically, when the sub-channels #n, #n+1, #n+2, and #n+3 areallocated to a specific terminal, if the control channel is transmittedonly through the sub-channel #n, and the limited resource region for thecontrol channel within the sub-channel #n is insufficient, the controlchannel may be transmitted also in the region of the sub-channel #n+1.As described above, when the resource region for transmitting thecontrol channel is insufficient, the control channel may be allocated toadditional resources secured while increasing the sub-channel index. Onthe other hand, when the sub-channel of the largest index is firstallocated for transmission of the control channel among the sub-channelsallocated to a specific terminal, if the resource region of thecorresponding sub-channel is insufficient, the control channel may beallocated to additional resources secured while reducing the sub-channelindex.

FIGS. 8A and 8B are conceptual diagrams for describing a first exemplaryembodiment of channel multiplexing in a communication system accordingto the present disclosure.

Referring to FIG. 8A, illustrated is a case in which one sub-channel,which is a basic unit of data transmission, is allocated to each ofterminals (e.g., UE A, UE B, UE C, and UE D). The data channel and thecontrol channel of each terminal may be multiplexed within thesub-channel in the same manner as the option 3 of FIG. 7 describedabove.

Referring to FIG. 8B, illustrated is a case in which a plurality ofsub-channels #n, #n+1, and #n+2 are allocated to a specific terminal(e.g., UE A′), and one sub-channel #n+3 is allocated to another terminal(e.g., UE B′). In case of the specific terminal (i.e., UE A′), thecontrol channel is not multiplexed with the data channel in allsub-channels, and is multiplexed with the data channel only in asub-channel (e.g., sub-channel #n) having the smallest index among thesub-channels allocated to the terminal. Other sub-channels may be usedonly for transmission of data channel(s).

In case of the NR system, a basic unit of a resource for transmitting acontrol channel is a control channel element (CCE), and one CCE may becomposed of 6 resource element groups (REGs). One REG may consist of 1physical resource block (PRB, 12 subcarriers) in the frequency domainand 1 OFDM symbol in the time domain. The control channel may betransmitted by applying one of CCE aggregation levels 1, 2, 4, 8, and 16according to a code rate, etc. applied in consideration of the size ofcontrol information to be transmitted and the channel state. Also in theNR-V2X sidelink communication, a control channel may be transmitted inthe same manner, and a design of a sidelink control channel (i.e.,PSCCH) considering the size and structure of the sub-channel that is abasic unit of sidelink communication is required. Accordingly, exemplaryembodiments of the present disclosure propose a PSCCH resource mappingmethod considering the size and structure of the sub-channel.

The basic unit of resource allocation in the NR-V2X sidelinkcommunication is a slot in the time domain and 10, 15, 20, 25, 50, 75,or 100 PRBs in the frequency domain (other values may be added). Also, aPSCCH within a sub-channel may be transmitted through 2 or 3 OFDMsymbols. Currently, the NR-V2X system supports at least the option 3scheme of FIG. 7 as the PSCCH and PSSCH multiplexing scheme. Therefore,an appropriate PSCCH resource mapping method considering afrequency-axis size of a sub-channel, a time duration of the PSCCH, andthe multiplexing scheme of the PSCCH and PSSCH is needed.

In an exemplary embodiment, a frequency start position may be determinedso that one or a plurality of CCEs can be mapped in the sub-channel inconsideration of the frequency-axis size of the sub-channel and thenumber of OFDM symbols for PSCCH transmission in the sub-channel. First,CCEs may be defined in units of 6 PRBs in the time and frequency domainfrom a first PRB within the sub-channel. In this case, resourcesremaining in the frequency domain may not be used as CCEs, but may beused for data transmission, or may be left empty. For example, w % benthe frequency-axis size of one sub-channel is determined as 10 PRBs andthe PSCCH is transmitted through 2 OFDM symbols, 6 PRBs may constituteone CCE in units of 3 PRBs in the frequency domain and in units of 2OFDM symbols in the time domain from the first PRB as a start point. Asdescribed above, when configuring the CCE in units of 3 PRBs in thefrequency domain, a total of 9 PRBs constitute the CCEs, and theremaining 1 PRB in the sub-channel may not be used as a CCE and may beused for data transmission or left empty. According to the variousfrequency-axis sizes of the sub-channel, CCEs may be configured in unitsof 6 PRBs in the time and frequency domains based on the first PRBwithin the sub-channel, the remaining PRBs that do not constitute theCCE within the sub-channel may be used for data transmission or leftempty. Through this, the terminal may implicitly find out theconfiguration of CCEs based on the preconfigured frequency-axis size ofthe sub-channel, thereby obtaining information of control channel.Alternatively, a method of configuring CCEs by using the last PRB as astart point may also be applied instead of the first PRB.

Since the control information includes scheduling information of dataand retransmission of the control information is difficult as comparedto data information, the control channel may be usually transmitted witha higher transmission power than the data channel. In addition, in thesidelink communication, since the control channel is monitored by allterminals, it is usually transmitted with a higher transmission powerthan the data channel. In this case, if the configuration of the CCEsfor transmission of the control channel starts from the first PRB or thelast PRB, the control channel may be necessarily mapped to one side ofthe sidelink frequency axis. In general, due to the characteristics ofthe control channel transmitted with a higher transmission power thanthe data channel, interferences on adjacent sub-channels due to in-bandemission (IBE) may be greater than that of the data channel.

Accordingly, in an exemplary embodiment, CCEs used for transmission ofthe control channel may start at a position obtained by applying apredetermined offset to the first PRB instead of a position of the firstPRB of the sub-channel. The corresponding start position may beimplicitly determined according to the sub-channel size. Morespecifically, at least one PRB(s) may be given as an offset (i.e.,frequency-axis offset) in at least one of both ending frequencies of thesub-channel, and then CCEs may be configured in units of 6 PRBs in thetime and frequency domains. In this case, the frequency-axis offset maybe implicitly determined according to the frequency-axis size of thesub-channel and the number of OFDM symbols used for PSCCH transmission.More specifically, the frequency-axis offset applied to CCEs may beimplicitly determined through the following procedure.

1. Determine the size X of PRBs in the frequency domain constituting theCCE according to the number of OFDM symbols used for PSCCH transmission.

A. When two OFDM symbols are used, X=3; When 3 OFDM symbols are used,X=2.

2. Determine the number of N's satisfying N*X<M by considering thefrequency-size M of the sub-channel.

3. Calculate R=floor ((M−N*X)/2).

A. When R=0, N is decreased by 1, and substituted into the equation ofthe step 2.

B. When R>0, set the frequency-axis offset value for the start positionof CCEs within the sub-channel to R.

FIG. 9 is a conceptual diagram for describing a second exemplaryembodiment of channel multiplexing in a communication system accordingto the present disclosure.

Referring to FIG. 9, the frequency-axis size of the sub-channel may beconfigured to be 10 PRBs, and the number of OFDM symbols for PSCCHtransmission may be configured to be 3. In this case, one CCE mayconsist of 2 PRBs in the frequency domain and 3 OFDM symbols in the timedomain. Therefore, N=2 and R=2 may be obtained as a result ofcalculation by applying the corresponding values (i.e., M=10, X=3) tothe above procedure. Accordingly, the frequency-axis start position forCCE configuration may be configured from a position having an offset of2 PRBs, and 2 CCEs may be configured within one sub-channel. In thiscase, there may be an offset of 2 PRBs also on the opposite side of theCCE start position within the sub-channel. Since 4 PRBs remain in thefrequency domain, there may be resources in which one CCE may be furtherconfigured. However, when one CCE is further configured in the remaining4 PRBs, a control channel exists at one end of the sub-channel, whichmay adversely affect IBE mitigation. Therefore, in order to have PRBoffsets for the IBE mitigation at both ends of the frequency of thesub-channel, it may be preferable to configure the resources as shown inFIG. 9.

In another exemplary embodiment, 1 PRB offset may be always appliedwithout calculating the PRB offset for the CCE start position throughthe above-described procedure. In this case, since the same offset isalways applied regardless of the frequency-size of the sub-channel, aseparate calculation procedure is not necessary. However, in case ofconfiguring CCEs with 1 PRB offset, even when the frequency resourcesrequired for CCE configuration remain in the frequency domain, if theadditional configuration of the corresponding CCEs makes the PRB offsetfor IBE mitigation not exist, the corresponding CCE may not beconfigured. For example, in the case of FIG. 9, if the CCE is configuredwith 1 PRB offset, 3 PRBs may be left upward, and additional CCEconfiguration may be possible. However, when the additional CCE isconfigured, since there is no offset in one side of the sub-channel, theIBE problem due to the control channel transmission may occur.Therefore, in this case, it may be preferable not to configure thecorresponding CCE.

On the other hand, when a plurality of sub-channels are allocated to oneterminal, only CCEs configured within one sub-channel may beinsufficient for PSCCH transmission. In this case, CCEs in a sub-channeladded while increasing the index of the sub-channel may be used forPSCCH transmission. In this case, the frequency-axis offset may becalculated again in consideration of the size of all the allocatedsub-channels, and CCEs may be configured without a boundary separationbetween the sub-channels. Alternatively, even when a plurality ofsub-channels are allocated, CCEs may be configured in the same mannerwithin each sub-channel, and CCEs used for actual PSCCH transmission maybe mapped in consideration of the entire plurality of sub-channels.

A method proposed in the present disclosure is for CCE configuration forcontrol channel transmission, and the actual PSCCH may be mapped to anarbitrary location in the configured CCEs. Not all CCEs are used for thePSCCH transmission, and some unused CCEs may exist.

In the NR-V2X sidelink communication, a plurality of sub-channels may beallocated to a specific terminal within a specific time unit (e.g.,hereinafter, a slot for convenience), but a plurality of time units(hereinafter, multiple slots for convenience) may also be allocated.When a plurality of slots are allocated for data transmission of aspecific terminal, the corresponding terminal should perform blinddetection on the plurality of slots to identify whether a controlchannel is transmitted. In this case, the complexity of the terminal mayincrease.

Accordingly, in an exemplary embodiment, when a plurality of slots areallocated for data transmission to a specific terminal, a controlchannel may be transmitted only within a specific slot among theplurality of allocated slots. More specifically, the specific slot maybe a slot having the smallest index, the largest index, or astatically-determined index among the plurality of slots allocated tothe corresponding terminal. When a plurality of sub-channels and aplurality of slots are simultaneously allocated to a specific terminal,a transmission position of a control channel within a correspondingresource region may be limited to a specific sub-channel index and aspecific slot index. For example, a control channel transmission regionmay be limited to a region within a sub-channel having the smallestindex in a slot having the smallest index. In this case, if there areinsufficient resources for transmission of the control channel in thecorresponding region, the index of the sub-channel may be preferentiallyincreased, and then the index of slot may be increased to configure thecontrol channel resource region.

Resource Reservation for Sidelink Communication

In the NR-V2X sidelink communication, resource configuration for datatransmission and reception between terminals may be performed based onsensing operations of the terminals. In this case, for the sensingoperation, the terminal may refer to information of control channels ofother terminals through a decoding process. Accordingly, the terminalmay reserve a resource to be used for data communication and notify itin advance to avoid collision of data transmission and reception betweenother terminals. In general, signaling for the resource reservation istransmitted by a terminal that intends to use the correspondingresource, and other terminals, including a terminal receiving datathrough the resource, may also monitor the resource reservationsignaling to refer to future resource use. In this case, the resourcereservation method may vary according to a case when retransmission isperformed according to HARQ feedback information for data transmissionand a case when initial transmission and retransmission are performed apredetermined number of times without HARQ feedback (i.e., blindretransmission).

In general, when retransmission is performed according to HARQ feedbackinformation for data transmission, control information may be configuredby additionally including information on a resource reserved for thenext retransmission in the scheduling information required for the datatransmission. For example, in case of initial transmission of data,control information including scheduling information for the initialtransmission may be configured to also include information on a resourcereserved for a first retransmission, and the first retransmission ofdata may be performed through the reserved resource when the HARQfeedback information for the corresponding data transmission indicatesNACK. In this case, the control information including the schedulinginformation for the first data retransmission may also includeinformation on a resource reserved for a second retransmission. In thismanner, the reserved resource information for the next transmission maybe sequentially included in the control information for the current datatransmission.

On the other hand, when initial transmission and retransmission areperformed a predetermined number of times without HARQ feedback for datatransmission, in addition to the method of including only theinformation of the resource reserved for the next transmission in thecontrol channel for current data transmission as described above, amethod of reserving resources needed for all transmissions at once maybe used. In this case, information on the resources reserved for aplurality of remaining retransmissions may be included in the controlinformation for initial data transmission, or separate controlinformation may include information on resources reserved for initialtransmission and multiple retransmissions.

When configuring information on a resource reserved for datatransmission at the next transmission time (hereinafter referred to as‘second data transmission time’) with reference to the current datatransmission time (hereinafter referred to as ‘first data transmissiontime’), the size of the necessary control information may be reducedrelatively, and may respond more flexibly to a varying channel andtraffic condition. Exemplary embodiments of the present disclosure mayprovide methods for efficiently signaling information on the reservedresource, when the control information for data transmission at thefirst data transmission time includes information on the resourcereserved for data transmission at the second data transmission time.

Hereinafter, it is assumed that the control information for datatransmission at the first data transmission time includes schedulinginformation for data at the first data transmission time, and thecorresponding information includes time and frequency resources(hereinafter, ‘first data transmission resource’) used for the datatransmission.

In an exemplary embodiment, information on a resource (hereinafterreferred to as ‘second data transmission resource’) reserved for datatransmission at the second data transmission time may be signaled as anoffset with respect to the data transmission resource (i.e., first datatransmission resource) at the first data transmission time. Morespecifically, a time and frequency difference of the position of thesecond transmission resource may be indicated based on the position ofthe first transmission resource. The time and frequency difference maybe represented in units of a specific time resource unit (e.g., symbol,mini-slot, slot, subframe, or frame) and in units of a specificfrequency resource unit (e.g., subcarrier, resource block, orsub-channel).

In another exemplary embodiment, a predetermined processing may berequired to prepare for data transmission at the second datatransmission time after data transmission at the first data transmissiontime, and in general, a time required for the processing may bepredicted in advance, and may be preconfigured. In this case, in orderto indicate the difference between the first data transmission resourceat the first data transmission time and the second data transmissionresource at the second data transmission time, a time resource offset(e.g., time periodicity) may be used as a predetermined fixed value, avalue configured semi-statically through system information orterminal-specific (i.e., UE-specific) RRC signaling, or a valuetransmitted separately through a specific channel, and only a frequencyresource offset may be signaled, thereby reducing a signaling overhead.In this case, ‘+’ or ‘−’ may be applied as the frequency resource offsetwith reference to the first data transmission resource. In this case,only one of ‘+’ and ‘−’ may be applied. When only one of ‘+’ and ‘−’ isapplied, the offset may be applied only in a specific direction based onthe initial resource, and thus may deviate from the resource region fordata transmission. Therefore, when only one of ‘+’ and ‘−’ is applied,this problem may be solved by applying a modulo operation based on thenumber of total frequency resource units within the resource region fordata transmission.

In another exemplary embodiment, a plurality of time resource offset(e.g., time periodicity) values may be configured semi-statically to theterminal in advance through system information or UE-specific RRCsignaling, and one value among the values may be dynamically selected.In this case, the signaling overhead can be reduced.

In yet another exemplary embodiment, a predetermined fixed value may beconfigured as the time resource offset (or, time periodicity), or asemi-static value may be configured through system information orUE-specific signaling as the time resource offset (or, timeperiodicity), and an offset applied in addition to the time resourceoffset (or time periodicity) may be signaled when configuring the seconddata transmission resource. In this case, it may be preferable that atime resource unit (hereinafter referred to as a ‘second time resourceunit’) smaller than a specific time resource unit (hereinafter referredto as a ‘first time resource unit’) representing the time resourceoffset (or time periodicity) is applied to the additional offset. Thesecond time resource unit may be applied as ‘+’ or ‘−’ for the timeresource offset represented by the preconfigured first time resourceunit. For example, in case that the time resource offset (or timeperiodicity) is configured in units of 1 frame, when configuring thesecond data transmission resource, an additional offset configured inunits of the second time resource unit, such as a subframe or a slothaving ‘+’ or ‘−’, may be applied with reference to the time resourceoffset (or time periodicity).

Meanwhile, when configuring the second data transmission resourcethrough the offset with reference to the first data transmissionresource, there may be a limit in a configuration range when consideringa signaling overhead. Accordingly, in an exemplary embodiment, thesecond data transmission resource may be configured by multiplying theoffset by a specific frequency interval. When the second datatransmission resource is configured by multiplying the offset by aspecific frequency interval, a wider range of resource configuration maybe made possible. However, since it is configured in multiples of thespecific frequency interval, detailed resource configuration may bedifficult. Therefore, in an exemplary embodiment, when the second datatransmission resource is configured by multiplying the offset by aspecific frequency interval, the receiving terminal may perform blinddetection on a control channel between a frequency position obtained byapplying the corresponding offset (i.e., the offset obtained bymultiplying the originally-signaled offset by the specific frequencyinterval) and a frequency position obtained by applying an offsetsmaller than the corresponding offset. More specifically, when offsetvalues of {−2, −1, 0, 1, 2} are defined, and the specific frequencyinterval is 2 sub-channels, the range of frequency positions that can beconfigured by the offset values according to the above-described schememay be increased to {−4, −2, 0, 2, 4}. In this case, when a frequencyposition required for actually configuring the second data transmissionresource is ‘3’, ‘2’ may be signaled as the offset. The terminal mayobtain a frequency position ‘4’ by multiplying the offset (i.e., ‘2’) bythe frequency interval (i.e., ‘2’), and perform blind detection on acontrol channel between the corresponding frequency position ‘4’ and thefrequency position corresponding to the smaller offset (e.g., ‘3’).Through the above-described scheme, the complexity of the receivingterminal may be increased, but the second data transmission resource maybe more efficiently configured.

The specific frequency interval may be determined in advance, or may beconfigured through system information, UE-specific RRC signaling, or aseparate specific channel. Alternatively, a frequency interval allocatedfor data transmission in the first data transmission resource may beused as the specific frequency interval. In the exemplary embodiment ofthe present disclosure, the unit of the specific frequency interval islimited to a sub-channel, but other basic frequency units such assubcarriers and resource blocks may also be applied as the unit of thespecific frequency interval. In addition, although the above-describedexemplary embodiments have described a resource configuration method inthe frequency domain, the same may be applied also to the resourceconfiguration in the time domain.

Considering the signaling overhead in the method of signaling the timeor frequency offset with reference to the first data transmissionresource, it may be difficult to inform the accurate position of thesecond data transmission resource when the actual position of the seconddata transmission resource is out of the range that can be configuredthrough the signaling. To solve this, a specific value may be set toindicate that the corresponding resource is out of the signaling rangeby the offset. More specifically, when configuring the second datatransmission resource by using the offset with reference to the firstdata transmission resource, if there is a limit to the size of controlinformation for configuring the second data transmission resource, therange of the offset values may be limited according to the size of thecontrol information. Accordingly, when the position of the second datatransmission resource is out of the signaling range using the offsetwith reference to the first data transmission resource, it may benotified to the terminal that the position of the second datatransmission resource does not exist in the corresponding signalingrange. In this case, when the control information for configuring theposition of the second data transmission resource indicates a specificstate (e.g., specific value), it may indicate that the position of thesecond data transmission resource is out of the signaling range.Alternatively, a separate indicator may be used to indicate that theposition of the second data transmission resource is out of thesignaling range. When it is determined that the information indicatingthe position of the second data transmission resource is out of thesignaling range, the receiving terminal should perform blind detectionto find the second data transmission resource outside the signalingrange. Alternatively, a direction (e.g., ‘+’ offset direction or ‘−’offset direction) out of the position signaling range of the second datatransmission resource may be indicated with reference to the first datatransmission resource, together with the information indicating that theposition of the second data transmission resource is out of thesignaling range. Accordingly, since the terminal only needs to perform ablind detection operation for finding the position of the second datatransmission resource in the ‘+’ or ‘−’ direction out of the signalingrange, the number of blind detections may be reduced. Alternatively,when it is determined that the position of the second data transmissionresource is out of the signaling range, it may be determined that thesecond data transmission resource has been released. In this case, theterminal may determine that the second data transmission resource doesnot exist separately, and may perform a normal data reception operation.

Release of Reserved Sidelink Resources

As described above, in the NR-V2X, resources for initial transmission orretransmission of sidelink data may be reserved. When it is no longernecessary to use the second data transmission resource at the seconddata transmission time, the reservation of the second data transmissionresource may be released to allow other terminals to use the second datatransmission resource. In order to release the reservation of the seconddata transmission resource, a terminal (hereinafter, ‘reservationterminal’ for convenience) that has reserved the second datatransmission resource may transmit a separate release signal to otherterminals. Alternatively, when other terminals monitor HARQ feedbackinformation for data transmitted by the reservation terminal, and theHARQ feedback information for the data transmitted by the reservationterminal indicates ACK, it may be determined that the second datatransmission resource reserved by the reservation terminal will not beused for data transmission of the reservation terminal. However, thesecond data transmission resource reserved by the reservation terminalmay be used for initial transmission of data other than retransmissionof the data transmitted at the first data transmission time. In thiscase, other terminals determining whether the reservation of the seconddata transmission resource is released through monitoring of the HARQfeedback information cannot determine whether the corresponding seconddata transmission resource will be used for retransmission of the datatransmitted at the first data transmission time or used for initialtransmission of data other than the previous data. If the number ofretransmissions including the initial transmission of the data ispredetermined, it may be implicitly determined that the second datatransmission resource will be used for initial transmission of dataother than the previous data after the maximum number ofretransmissions. However, in the case of the second data transmissionresource before the maximum number of retransmissions, even when thefeedback information for the previous data indicates ACK, it may bedifficult for other terminals to determine whether the second datatransmission resource will be used for initial transmission of dataother than the previous data. Therefore, in an exemplary embodiment, thesignaling for the second data transmission resource may includeinformation on whether the corresponding second data transmissionresource can be used only for retransmission of the data transmitted atthe first data transmission time or can be used for initial transmissionof data other than the previous data. More specifically, when thereservation terminal indicates that the corresponding second datatransmission resource can be used only for retransmission of the datatransmitted at the first data transmission time through a separateindication method, other terminals may perform monitoring on the HARQfeedback information for the data transmitted by the reservationterminal, and determine whether the HARQ feedback information for thecorresponding data indicates ACK. When the HARQ feedback information isdetermined to indicate ACK, other terminals may determine that thereservation of the corresponding second data transmission resource hasbeen released. On the other hand, when the corresponding second datatransmission resource is configured as capable of being used for initialtransmission of data other than the previous data, even if otherterminals determine that the HARQ feedback information for the datatransmitted by the reservation terminal indicates ACK through monitoringon the HARQ feedback information for the corresponding data, otherterminals may determine that the reservation of the corresponding seconddata transmission resource has not been released. In both of theabove-described cases, if the feedback information for the datatransmitted at the first data transmission time indicates NACK, theterminal may determine that the corresponding second data transmissionresource is to be used for retransmission of the data transmitted at thefirst data transmission time.

FIGS. 10 to 12 are conceptual diagrams for describing transmissionresource allocation in a communication system.

Referring to FIG. 10, when a control channel for data transmission at afirst data transmission time of a specific terminal (e.g., UE A)includes information on a second data transmission resource for datatransmission at a second data transmission time, and feedbackinformation for the data transmission at the first data transmissiontime indicates NACK, the corresponding second data transmission resourcemay be used for retransmission of the data transmitted at the first datatransmission time.

Referring to FIG. 11, when a control channel for data transmission at afirst data transmission time of a specific terminal (e.g., UE A)includes information on a second data transmission resource for datatransmission at a second data transmission time, but the second datatransmission resource is configured to be reserved only forretransmission of the specific terminal (i.e., UE A), if feedbackinformation for the data transmission at the first data transmissiontime indicates ACK, other terminals may determine that the reservationof the corresponding second data transmission resource has beenreleased, and use the second data transmission resource for datatransmission of other terminals.

Referring to FIG. 12, when a control channel for data transmission at afirst data transmission time of a specific terminal (e.g., UE A)includes information on a second data transmission resource for datatransmission at a second data transmission time, and the correspondingsecond data transmission resource is configured to be reserved forretransmission of the specific terminal (i.e., UE A) or initialtransmission of other data, even if feedback information for the datatransmitted at the first data transmission time indicates ACK, otherterminals may not determine that the reservation of the correspondingsecond data transmission resource has been released, and determine thatthe corresponding second data transmission resource will continue to beused for data transmission (initial transmission of the data other thanthe previous data of the specific terminal (i.e., UE A)).

In order to indicate whether the second data transmission resource canbe used only for retransmission of the data transmitted at the firstdata transmission time or can be used also for initial transmission ofdata other than the previous data, a separator indicator (e.g.,indication bit) may be added to the control channel including schedulinginformation of the first data transmission resource for the data andinformation on the second data transmission resource. Alternatively,control information may indicate the corresponding information when apart of the control information indicates a specific state (e.g., all‘0’s or ‘1’s). More specifically, the above-described information may berepresented by indicating that the offset for configuring the seconddata transmission resource is out of the signaling range. Alternatively,the indicator may be configured in form of additional informationapplied only in a specific mode. In this case, whether the systemoperates in the specific mode, that is, whether the second datatransmission resource is used only for retransmission for thetransmission data at the first data transmission time or for initialtransmission of data other than the previous data may be configured inadvance through system information or UE-specific RRC signaling. Morespecifically, when the second data transmission resource is configuredto be used not only for retransmission of data transmitted at the firstdata transmission time but also for initial transmission of data otherthan the previous data, periodicity information may be additionallyconfigured to periodically reserve the corresponding transmissionresources, so that the corresponding transmission resources are used forperiodical traffic transmission. In this case, the additionalperiodicity information itself may be transmitted together with theconfiguration information of the transmission resources. Alternatively,a set of periodicity information may be configured in advance throughsystem information, etc., and an index indicating specific periodicityinformation in the preconfigured set of the periodicity information maybe transmitted together with the configuration information of thetransmission resources.

When the configuration information of transmission resources and theperiodicity information (or index information indicating theperiodicity) are configured together, and thus the transmissionresources are periodically configured, the configured resources may besuitable for periodic traffic transmission. However, since the resourcesconfigured as described above are determined to be reserved for datatransmission, they may be excluded from a group of transmission resourcecandidates during resource sensing and selection for data transmissionresources of other terminals. When the data transmission resource isconfigured by combining the configuration information of transmissionresources and the periodicity information as described above, thecorresponding resources may be continuously and infinitely configuredaccording to the configured periodicity. Since the correspondingresources are determined to be reserved, they are also excluded from theresource sensing and selection process for data transmission resourcesof other terminals, so if they are not used for actual transmission,they may remain resources that are not actually used, resulting inresource waste. Accordingly, exemplary embodiments of the presentdisclosure propose a method for preventing the periodic resourcereservation from being configured infinitely by limiting application ofthe periodicity information when the configuration information oftransmission resources and the periodicity information are configured ascombined.

As a method of limiting the application of periodicity information, anupper limit of the number of resources to which the periodicityinformation is applied may be configured, or a timer may be configuredso that the periodicity information is applied only within theconfigured number of resources or until the timer expires. In this case,the configured upper limit of the number of resources to which theperiodicity information is applied or a value of the timer may bepreconfigured to the terminal through system information or UE-specificRRC signaling. Alternatively, information on a counter may betransmitted with the periodicity information, and the counter may bedecremented or incremented each time the periodicity information isapplied to resources. Accordingly, when the counter reaches 0 or aspecific value configured in advance through system information orUE-specific RRC signaling, the application of the periodicityinformation may be stopped. Alternatively, a specific state of aspecific field of control information including the configurationinformation of transmission resources and the periodicity informationmay indicate deactivation of the periodic resource configuration,without using the upper limit of the number of resources to which theperiodicity information is applied or the timer. More specifically, thespecific field of the control information may be a field indicating theperiodicity information, and the periodic resource configuration may bedeactivated through the periodicity information indicating a specificstate (e.g., a specific value (‘0’)). As another example, the specificfield of the control information may be a field indicating periodicityinformation preconfigured through system information or UE-specific RRCsignaling, and the deactivation of the periodic resource configurationmay be indicated when the indicated preconfigured periodicityinformation represents a specific state (e.g., a specific value (‘0’)).

When it is determined by other terminals that the reservation of thesecond data transmission resource by the reservation terminal has beenreleased, a priority for the preference of using the second datatransmission resource may be increased by a plurality of terminals, sothat a probability of collision between transmissions and receptions bythe plurality of terminals in the corresponding second data transmissionresource may increase rather. Accordingly, exemplary embodiments of thepresent disclosure propose a method for reducing collisions due toincreases in usage preferences by other terminals for the second datatransmission resource for which reservation has been released. Morespecifically, even when it is determined that the reservation of thesecond data transmission resource, which has been reserved by thereservation terminal, has been released, the priority for the usagepreference of the second data transmission resource may not beincreased. A plurality of terminals determining that the reservation ofthe second data transmission resource has been released may set thepriority of usage preference for the second data transmission resourceto be the same as the priority of other resources. That is, in theresource selection process, a method of not increasing a probability ofselecting the second data transmission resource as compared to otherresources may be applied. Alternatively, terminals capable of selectingand using the released second data transmission resource may be limited.When terminals capable of selecting and using the released second datatransmission resource are limited to some terminals according to aspecific criterion, the probability of collisions in the correspondingsecond data transmission resource may be reduced. As the specificcriterion that can be applied in this case, a distance between thereservation terminal and each terminal may be used. By using thedistance from the reservation terminal, the probability of collisions inthe corresponding second data transmission resource may be reduced bygiving a priority of using the released second data transmissionresource to terminals within a predetermined distance from thereservation terminal. Alternatively, a magnitude of a signal transmittedfrom the reservation terminal, such as RSRP, may be measured and appliedby each terminal. The priority of using the released second datatransmission resource may be given to terminals in which the signal ofthe reservation terminal is measured as having a value equal to orgreater than a predetermined value, thereby reducing the probability ofcollisions in the second data transmission resource. In this case, thedistance or the magnitude of the measurement signal, that can be used asa reference, may be determined in advance, configured statically orsemi-statically through system information, etc., or dynamicallyconfigured through a control channel, etc.

In the above description, the feedback information may be transmittedthrough a specific channel. More specifically, the specific channel maybe a physical sidelink feedback channel (PSFCH), which is a sidelinkfeedback transmission channel. In addition, the reservation signal, thecontrol signal for the separate indication method (i.e., indication onwhether or not the second data transmission resource is used only forretransmission of the data transmitted at the first data transmissiontime), etc., the periodicity information, or the data and controlinformation may be transmitted on specific channel(s). Morespecifically, the specific channels may be a physical sidelink sharedchannel (PSSCH) and a physical sidelink control channel (PSCCH), whichare sidelink data and control information transmission channels. In theabove exemplary embodiments, the first data transmission resource andthe second data transmission resource have been described, but these arefor convenience of description, and the exemplary embodiments of thepresent disclosure may be applied to reservation of more datatransmission resources. Meanwhile, the exemplary embodiments of thepresent disclosure have been described based on sidelink communicationbetween terminals, but are not limited to the sidelink communicationbetween terminals, and may be applied to general uplink and downlinkcommunications. The exemplary embodiments of the present disclosure havebeen described based on transmission and reception of sidelink data,control information, and feedback information, but are not limitedthereto.

Backward Indication

As described above, in the NR-V2X, the resources for initialtransmission or retransmission of sidelink data may be reserved. In thiscase, two or three transmission resources including a transmissionresource to be currently used may be reserved through one controlinformation. In this case, how many transmission resources can beconfigured by one control information may be predefined by the technicalspecification or configured by the base station to the terminals. Also,two or three transmission resources including the transmission resourceto be currently used may be configured only within a predetermined timeperiod. For example, when configuration of three transmission resourcesis possible, the three transmission resources may be defined as a firstdata transmission resource, a second data transmission resource, and athird data transmission resource. The control information transmittedtogether with data in the respective transmission resources may bedefined as first control information, second control information, andthird control information. In this case, when the first datatransmission resource and the second data transmission resource arelocated within a predetermined time period, but the third datatransmission resource is located out of the predetermined time period,the third data transmission resource may not be configured, and only thetwo data transmission resources located within the predetermined timeperiod, that is, the first data transmission resource and the seconddata transmission resource may be configured.

When a plurality of transmission resources are configured within apredetermined time period and a plurality of control information aretransmitted together with a plurality of data channels in the respectivetransmission resources, each control information may redundantlyindicate resource allocation for the plurality of transmission resourceswithin the predetermined time period. For example, when the first datatransmission resource, the second data transmission resource, and thethird data transmission resource are configured within a predeterminedtime period, and the first control information, the second controlinformation, and the third control information are transmitted togetherwith data in the respective transmission resources, each of the firstcontrol information, the second control information, and the thirdcontrol information may redundantly include resource allocationinformation for the first data transmission resource, the second datatransmission resource, and the third data transmission resource locatedwithin the predetermined time period. Through the configuration in thismanner, when a receiving terminal attempts to detect specific controlinformation within the predetermined time period, but a receptionthereof fails, the receiving terminal may identify configuration of theplurality of transmission resources through other control information.For example, even when the receiving terminal fails to receive thesecond control information, the receiving terminal may obtainconfiguration information of the first data transmission resource, thesecond data transmission resource, and the third data transmissionresource through the first control information and/or the third controlinformation. However, in this case, since the receiving terminal doesnot know which order the corresponding control information has among thefirst, second, and third control information, a method for solving theproblem is needed. Accordingly, exemplary embodiments of the presentdisclosure propose a method for adding information indicating whichorder the corresponding control information has among the plurality ofcontrol information.

More specifically, when it is possible to configure two transmissionresources within a specific time period, it may be indicated by using1-bit information whether the control information currently transmittedis the first control information or the second control information. Whenit is possible to configure three transmission resources within aspecific time period, it may be indicated by 2-bit information whetherthe control information currently transmitted is the first controlinformation, the second control information, or the third controlinformation.

As described above, if it is known to the receiving terminals whichorder each of the control information has within a specific time period,the receiving terminal can obtain the entire configuration informationof the plurality of transmission resources within the specific timeperiod even when receiving only some of the plurality of controlinformation within the specific time period, thereby reducing aprobability of data transmission failure of the corresponding terminalor a probability of collisions between transmission data of terminals,which may occur due to the failure to receive some control information.

In the above description, the control information may be transmittedthrough a specific channel. More specifically, the specific channel maybe first-stage control information (e.g., sidelink control information(SCI)) of the sidelink. In the above-described exemplary embodiments,the number of resources that can be configured within a specific timeperiod is limited to 2 or 3, but this is for convenience of description,and the above exemplary embodiments may also be applied to reservationof more data transmission resources.

FIG. 13 is a block diagram illustrating a configuration of an apparatusfor performing methods according to exemplary embodiments of the presentdisclosure.

The exemplary configuration illustrated in FIG. 13 may be applied to theabove-described transmitting terminal or receiving terminal, and thesame or similar structure may be applied to the base station.

Referring to FIG. 13, a terminal 1300 may include at least one processor1310, a memory 1320, and a transceiver 1330 connected to a network toperform communication. In addition, the terminal 1300 may furtherinclude an input interface device 1340, an output interface device 1350,a storage device 1360, and the like. The components included in theterminal 1300 may be connected by a bus 1370 to communicate with eachother. However, each component included in the terminal 1300 may beconnected to the processor 1310 through a separate interface or aseparate bus instead of the common bus 1370. For example, the processor1310 may be connected to at least one of the memory 1320, thetransceiver 1330, the input interface device 1340, the output interfacedevice 1350, and the storage device 1360 through a dedicated interface.

The processor 1310 may execute at least one instruction stored in atleast one of the memory 1320 and the storage device 1360. The processor1310 may refer to a central processing unit (CPU), a graphics processingunit (GPU), or a dedicated processor on which the methods according tothe exemplary embodiments of the present invention are performed. Eachof the memory 1320 and the storage device 1360 may be configured as atleast one of a volatile storage medium and a nonvolatile storage medium.For example, the memory 1320 may be configured with at least one of aread only memory (ROM) and a random access memory (RAM).

The at least one instruction may be configured such that the processor1310 performs each of the steps constituting the data transmissionmethod or data reception method according to the above-describedexemplary embodiments of the present disclosure, and all informationexchanged between the terminals or between the base station and theterminal may be transmitted or received through the transceiver 1330under the control of the processor 1310.

The exemplary embodiments of the present disclosure may be implementedas program instructions executable by a variety of computers andrecorded on a computer readable medium. The computer readable medium mayinclude a program instruction, a data file, a data structure, or acombination thereof. The program instructions recorded on the computerreadable medium may be designed and configured specifically for thepresent disclosure or can be publicly known and available to those whoare skilled in the field of computer software.

Examples of the computer readable medium may include a hardware devicesuch as ROM, RAM, and flash memory, which are specifically configured tostore and execute the program instructions. Examples of the programinstructions include machine codes made by, for example, a compiler, aswell as high-level language codes executable by a computer, using aninterpreter. The above exemplary hardware device can be configured tooperate as at least one software module in order to perform theembodiments of the present disclosure, and vice versa.

While the exemplary embodiments of the present disclosure and theiradvantages have been described in detail, it should be understood thatvarious changes, substitutions and alterations may be made hereinwithout departing from the scope of the present disclosure.

What is claimed is:
 1. A sidelink (SL) communication method performed bya first terminal in a communication system, the SL communication methodcomprising: transmitting, to a second terminal, first sidelink controlinformation (SCI) indicating a first transmission resource and one ormore second transmission resources; transmitting a first redundancyversion (RV) of a first transport block (TB) to the second terminalthrough the first transmission resource; and when a first configurationindicator is not set, transmitting a second RV of the first TB to thesecond terminal through a resource among the one or more secondtransmission resources; and when the first configuration indicator isset, transmitting the second RV of the first TB or a first RV of asecond TB other than the first TB to the second terminal through aresource among the one or more second transmission resources.
 2. The SLcommunication method according to claim 1, wherein the firstconfiguration indicator is set or not set through a terminal-specificradio resource control (RRC) message.
 3. The SL communication methodaccording to claim 1, further comprising receiving, from the basestation, configuration information including a list of candidateperiodicities for the one or more second transmission resources, whereinwhen the first configuration indicator is set, the first CSI furtherincludes an index indicating a reservation periodicity of the one ormore second transmission resources among the list of candidateperiodicities.
 4. The SL communication method according to claim 3,wherein the configuration information is received through aterminal-specific RRC message.
 5. The SL communication method accordingto claim 3, wherein a number of the one or more second transmissionresource(s) is limited by a counter.
 6. The SL communication methodaccording to claim 3, further comprising: transmitting second SCIincluding an index indicating a reservation periodicity set to 0 for theone or more second transmission resources; and releasing reservation ofthe one or more second transmission resources.
 7. A sidelink (SL)communication method performed by a second terminal in a communicationsystem, the SL communication method comprising: receiving, from a firstterminal, first sidelink control information (SCI) indicating a firsttransmission resource and one or more second transmission resources;receiving a first redundancy version (RV) of a first transport block(TB) from the first terminal through the first transmission resource;and when a first configuration indicator is not set, receiving a secondRV of the first TB from the first terminal through a resource among theone or more second transmission resources; and when the firstconfiguration indicator is set, receiving the second RV of the first TBor a first RV of a second TB other than the first TB from the firstterminal through a resource among the one or more second transmissionresources.
 8. The SL communication method according to claim 7, whereinthe first configuration indicator is set or not set through aterminal-specific radio resource control (RRC) message.
 9. The SLcommunication method according to claim 7, further comprising receiving,from the base station, configuration information including a list ofcandidate periodicities for the one or more second transmissionresources, wherein when the first configuration indicator is set, thefirst CSI further includes an index indicating a reservation periodicityof the one or more second transmission resources among the list ofcandidate periodicities.
 10. The SL communication method according toclaim 9, wherein the configuration information is received through aterminal-specific RRC message.
 11. The SL communication method accordingto claim 9, wherein a number of the one or more second transmissionresource(s) is limited by a counter.
 12. The SL communication methodaccording to claim 9, further comprising: receiving second SCI includingan index indicating a reservation periodicity set to 0 for the one ormore second transmission resources; and releasing reservation of the oneor more second transmission resources.